In automatic series production, motor vehicle wheels which have tubeless tires are usually filled with compressed air by means of an inflation machine. In so doing, the wheel rim with assembled tire is positioned on a suitable base plate which downwardly seals the wheel during the filling procedure. Positioned on the upper side of the tire is a filling bell which upwardly seals the tire and the rim and by which the side wall of the tire is pressed downwards to such an extent during the filling procedure that there is produced between the tire bead and wheel rim an annular gap through which the compressed air guided into the filling bell can flow into the tire. The compressed air which has been introduced presses the tire with considerable force against the supporting plate and the filling bell. Once the filling pressure has been attained, the filling bell is lifted, as a result of which the side walls of the tire move apart in an axial direction until the tire beads have assumed their respective seating positions on the rim. For a filling procedure of this type, the filling bell must have an opening, the diameter of which is large enough so that it does not abut against the wheel rim, but can be put over the wheel rim. On the other hand, however, the diameter of the opening must not be so big that the filling bell radially contacts the upper side wall of the tire outside its high point. In that case, the filling bell would obstruct the radial movement of the tire, which could result in the tire bead not springing correctly into its seat. If the sealing edge of the bell was located in the vicinity of the cover of the tire, the result might be a high degree of leakage and inaccuracy in the filling pressure. Thus, a filling bell is only suitable for a limited size range of motor vehicle wheels.
Thus, for example, only those tires which have a bead seat diameter in the region of two inch sizes can usually be filled using a filling bell of a specific size.
In order to be able to fill tires of a greater size difference by means of a tire filling station, it is known, inter alia from EP 1 125 772 B1 to use a tire filling bell which has at least two filling rings of different diameters, the smaller or the larger filling ring being used according to the size of the tire.
DE 198 01 455 A1 discloses a tire inflating device which has three filling rings and a rim sealing ring which is arranged inside the smallest filling ring and is expanded to the greater diameter required in each case by an adjusting device when one of the two larger filling rings is used.